On Wed, Sep 04, 2019 at 10:38:59AM -0700, Bart Van Assche wrote: > On 9/4/19 10:31 AM, Daniel Lezcano wrote: > > On 04/09/2019 19:07, Bart Van Assche wrote: > > > Only if CONFIG_IRQ_TIME_ACCOUNTING has been enabled. However, I don't > > > know any Linux distro that enables that option. That's probably because > > > that option introduces two rdtsc() calls in each interrupt. Given the > > > overhead introduced by this option, I don't think this is the solution > > > Ming is looking for. > > > > Was this overhead reported somewhere ? > I think it is widely known that rdtsc is a relatively slow x86 instruction. > So I expect that using that instruction will cause a measurable overhead if > it is called frequently enough. I'm not aware of any publicly available > measurement data however. https://www.agner.org/optimize/instruction_tables.pdf RDTSC, Ryzen: ~36 RDTSC, Skylake: ~20 Sadly those same tables don't list the cost of actual exceptions or even IRET :/
